1. Field of the Invention
This invention concerns cyclodextrinyl-containing organosilicon compounds, their preparation, their use, especially in textile finishing, and also crosslinkable compositions based on cyclodextrinyl-containing organosilicon compounds.
2. Description of the Related Art
Organosilicon compounds, especially organosilanes and organosiloxanes, are well known and widely used, for example as a softener.
Cyclodextrins are cyclic oligosaccharides constructed of 6, 7 or 8 α-(1-4)-linked anhydroglycose units. α-, β- and γ-Cyclodextrins prepared by enzymatic starch conversion differ in the diameter of their hydrophobic cavity and are generally useful for inclusion of numerous lipophilic substances.
Cyclodextrin derivatives are prepared by chemical modification of the OH groups of cyclodextrin. Examples of modifying chemistries are hydroxypropylation using propylene oxide and methylation using methyl halides. The cyclodextrin derivatives thus obtained are significantly more soluble in water than native cyclodextrins and are capable of solubilizing inherently water-insoluble, hydrophobic substances in an aqueous medium by inclusion and formation of water-soluble complexes. DE-A 195 20 967 describes reactive cyclodextrin derivatives with at least one nitrogenous heterocycle which are useful for finishing textile materials or leather. Whereas unsubstituted or methyl- or hydroxypropyl-substituted cyclodextrins can only be fixed on textile substrates with the aid of binder systems, the monochiorotriazine derivative is (completely analogously to reactive dyes) capable of forming a genuine covalent bond with the OH groups of the cellulosic textile substrate. However, this generally requires “dyeing conditions”; that is, cellulose is generally only efficiently reactive for entering this bond after activation with alkali at elevated temperature. The hydrolysis of the chlorotriazine radical occurs as a competing reaction. It is known from the dyeing arts that reactive dyes therefore usually only go on in a 50% yield or so, the other half being lost through hydrolysis. A similar ratio is likely when reacting a cellulosic textile substrate with a monochlorotriazine-functional cyclodextrin.
Organosilicon compounds having covalently attached cyclodextrin residues are known in the field of chromatographic separation analysis. The cyclodextrin-containing polymers immobilized on a carrier material such as silica gel, serve especially as chiral stationary phases for enantiomer separation of organic compounds. In addition, specific siloxane-cyclodextrin copolymers find use as contact lens material or in ion-sensitive electrodes. See for example DE-A-43 24 636, U.S. Pat. Nos. 5,268,442, 5,403,898 and EP-A 586 322. All cases involve time-consuming multistep syntheses based on hydrosilylation reactions, which give desired materials in a low yield only.
Block copolymers having cyclodextrin in the polymer chain are known. The copolymers can be formed in two ways. M. B. Ali et al., Mater. Sci. Eng. C 1998, C6, 53 react one or more hydroxyl groups of the cyclodextrin molecule directly with hydromethylsiloxy-containing polyorganosiloxanes by elimination of hydrogen. The materials obtained find application as membrane gels in ion-sensitive electrodes. Maciejewski et al. PL-B-178362, by contrast, prefer the polycondensation of OH-containing cyclodextrin derivatives with chlorosilanes which proceeds with HCl elimination. Both approaches lead to the formation of cyclodextrin-silicone block copolymers in which the cyclodextrin molecule is an integral constituent of the polymer network and acts as a bonding link or branching site between siloxane blocks. The SiOC linkage means that the copolymers are not stable to hydrolysis under nonneutral conditions. Further disadvantages of the processes mentioned are first, the release of hydrogen, which entails appreciable problems on an industrial scale, and also in the case of PL-B-178362, a nonuniform copolymeric composition, which is solely controlled by statistical effects.
As well as the processes mentioned above, there are isolated examples of linkages via carboxylic or carbonic acid derivatives in the literature. Similarly, acid-catalyzed epoxide-ring opening via the hydroxyl groups of the cyclodextrin molecule has already been described in the past. Examples are S. K. Young et al. (Polym. Prepr. 2001, 42, 162), M. Tanaka et al. (Fresenius Z. Anal. Chem. 1983, 316, 54) and also DE-A-42 08 402. Cost-intensive reagents as well as multistep synthetic processes are again disadvantages.